In the telecommunications field, the use of relatively high permeability ferrimagnetic materials, in the range of 5,000 to 20,000 perm, is required in a number of systems. However, the operating environments for these telecommunication devices encompass substantial environmental variances. For example, the temperature in which telecommunication devices must operate may range from -20.degree. C. to as much as 80.degree. C.
In existing ferrimagnetic materials, 40 degree temperature fluctuations often produce a variance in magnetic permeability of more than 20%. Such variance would often limit or preclude operation of the device. Specifically, it has been found that at low temperatures, that magnetic permeability substantially decreases and this change in an operating characteristic of the ferrimagnetic component jeopardizes the communications network.
Generally, the presence of extremely large grain sizes in a ferrimagnetic material has been disfavored. The prior art has provided numerous methods for obtaining substantially uniform grain size in a ferrimagnetic material.
For example, U.S. Pat. No. 5,498,361 discloses a ferrite having an average grain diameter of 5 to 50 microns, wherein the coefficient of variation of grain size is small. Further, the '361 patent discloses that upon forming a mixture, the mixture is combined with a binder and granulated to a mean particle size of 150 microns through a spray dryer and compacted. Subsequently, the compacted material is sintered.
Similarly, U.S. Pat. No. 3,948,785 discloses a method of forming a ferrimagnetic material, which method includes calcining, milling, binder addition and sintering. Each of these processes are performed on a single composition.
However, the need still exists for a ferrimagnetic material that exhibits a relatively stable magnetic permeability throughout a relatively large temperature range. The need also exists for a ferrimagnetic material that has a suppressed or at least reduced primary and secondary magnetic permeability maximums. A further need exists for a method of manufacturing such a ferrimagnetic material.